Process for preparing antimicrobial polymeric materials using irradiation

ABSTRACT

Polyamide, polyurea, polyhydrazide, and polyurethane materials having substantially modified surfaces which are antimicrobial are disclosed. The disclosure also relates to selective ultraviolet (UV) photon irradiation, high energy electron irradiation low energy electron irradiation for preparing such antimicrobial, polymeric materials. The disclosure further provides methods for controlling microorganisms, and products made from the antimicrobial, polymeric materials of this invention.

This a continuation Ser. No. 07/849,375filed May 4, 1992, now abandonedwhich is a continuation-in-part application of application Ser. No.07/431,583, filed Nov. 3, 1989, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to certain polymeric materials havingsubstantially modified surfaces which are inherently antimicrobial. Theinvention also relates to selective irradiation and chemical reducingprocesses for preparing the antimicrobial materials of the invention,methods of using such antimicrobial materials to control microorganisms,and products and devices comprising such antimicrobial materials.

2. Description of the Prior Art

Although there is no disclosure of imparting antimicrobial properties,laser irradiation of fibers, yarns, and nonwoven materials is known.PCT. Application WO 87/03021, published May 5, 1987, discloses theirradiation of such materials to form depressions and elevations on thesurface which improves the material's adhesiveness, frictionalresistance and absorptive capacity.

Polyamide materials can also be irradiated with electron energy ortreated chemically for grafting purposes, or for improving certainmechanical properties. United Kingdom Patent, 1,078,457, disclosestreating polyamide materials with stabilizers such as sodium andpotassium borohydride for protecting the materials from discolorationand loss of mechanical strength when exposed to heat or light. Nablo,U.S. Pat. No. 3,774,706, discloses a process of using substantiallymonochromatic, short-period, high intensity electron beams at a dosagerate considerably in excess of 10⁷ rads/second to bulk-sterilize a widerange of substances. Nablo, U.S. Pat. No. 4,211,622, discloses usingelectron energy to graft phosphorous or halogen-rich double bondedmolecules into materials such as nylon in order to impart flameretardant properties. Tamura et al., U.S. Pat. No. 4,291,142, disclosescrosslinked aromatic polyamide films which may be crosslinked by meansof heat, ultraviolet (UV) rays, or electron beams. The crosslinked filmshows an increased resistance to thermal decomposition. Calcaterra etal., U.S. Pat. No. 4,810,567, discloses a class of antimicrobial fabricshaving one or more antimicrobial agents covalently bonded to a graftcopolymer of the fabric. The graft copolymer may be formed by electronbeam irradiation of a fabric impregnated with a vinyl monomer.

It is also known that antimicrobial properties can be imparted tocertain types of acrylic polymers, fibers and fabrics. Pardini, U.S.Pat. No. 4,708,870, discloses an antimicrobial composition of a) atleast 85% by weight acrylonitrile, b) up to about 13% by weight of aneutral ethylenically unsaturated monomer, and c) from-about 0.1 to 10%by weight of a protonated amine containing compound. The composition isformed by copolymerization of the acrylic protonated amine comonomerand/or by use of protonated amine end groups.

In accordance with the present invention, it has now been discoveredthat certain polymeric materials having substantially modified surfacesare antimicrobial. It has also been discovered that selectiveultraviolet (UV) photon irradiation, electron irradiation, or chemicalreducing agents can impart this property to the polymeric material.

SUMMARY OF THE INVENTION

The present invention relates to certain polymeric materials havingsubstantially modified surfaces which are inherently antimicrobial.These antimicrobial materials include natural and synthetic polyamides,polyureas, polyhydrazides, polyurethanes and copolymers and blendsthereof. Each of these materials has a surface containing a sufficientamount of corresponding functional groups, amines and/or hydrazines, toimpart antimicrobial activity to the surface.

The antimicrobial, polymeric materials of this invention may be formedby the following methods:

1) ultraviolet (UV) photon irradiation,

2) high energy electron irradiation,

3) low energy electron irradiation, and

4) chemical reduction.

This invention also relates to such irradiation and chemical reductionprocesses for forming antimicrobial, polymeric materials. Preferably,the UV photons have a wavelength of no greater than 222 nm with anenergy density of at least 300 mJ/cm². Sources of suitable UV photonirradiation include lasers and UV lamps. For electron irradiation,electrons having a kinetic energy of at least 6 eV, at an energyabsorption from the electrons of at least 10,000 erg/cm³ of irradiatedvolume may be used. Preferably, the electrons have a kinetic energybetween 100 to 5000 eV, at an energy absorption from the electrons of50,000 to 250,000 erg/cm³ of irradiated volume. For chemical reduction,the material is treated with an effective reducing agent to form thecorresponding functional groups on the surface of the material.

This invention further relates to methods for controlling microorganismsusing the antimicrobial materials of this invention, and to productscomprising the antimicrobial materials of this invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to processes involving selective UV photonirradiation, electron irradiation, or chemical reducing agents toprepare a polymeric material having a substantially modified surfacethat is inherently antimicrobial. By the term "inherently antimicrobial"it is meant that the addition of adventitious materials such asbiocides, disinfectants, etc., is not necessary for the polymericmaterial to demonstrate antimicrobial activity.

The term "antimicrobial" as used herein, refers to the reduction of aKlebsiella pneumoniae microbial population by at least 99% in numberafter 24 hours exposure to the irradiated material produced by theprocesses of this invention using the Shake Flask Test described, infra.

In accordance with this invention, it has now been found that certainpolymeric materials having substantially modified surfaces areantimicrobial. The polymeric materials may be in such forms as, forexample, films, fibers, fibrids, powders, or articles made therefrom.

One method for forming such materials involves the excision of carbonylgroups (C═O) from the surface of a material comprising an organicpolymer having repeating units of the structural formula, ##STR1##wherein, the polymer is selected from the group consisting of asynthetic or natural polyamide, poly-urea, polyhydrazide, andpolyurethane. This excision method may be performed by irradiation andinvolves excising enough carbonyl groups to form a sufficient amount ofa new polymer species which imparts antimicrobial activity to thesurface of the material.

Where the polymer is a synthetic polyamide, (R¹ is either an alkyl groupor an aryl group, R² is either an alkyl group or an aryl group, and R³is either hydrogen, an alkyl group, or an aryl group), or a naturalpolyamide, (R¹ is R₄ --CH(NH), R² is an alkyl group, and R³ ishydrogen), excision of the carbonyl groups forms a surface Containing asufficient amount of amine groups to impart antimicrobial activity. Forthe synthetic polyamide, R³ is preferably hydrogen, because the hydrogenbonding provides the polymer with higher thermal stability andmechanical properties.

Where the polymer is a polyurea, (R¹ is NH, R² is either an alkyl groupor an aryl group, and R³ is hydrogen), excision of the carbonyl groupsforms a surface containing a sufficient amount of amine and hydrazinegroups to impart antimicrobial activity.

Where the polymer is a polyhydrazide (R¹ is either an alkyl group or anaryl group, R² is NHC═O, and R³ is hydrogen), excision of the carbonylgroups forms a surface containing a sufficient amount of hydrazinegroups to impart antimicrobial activity.

Where the polymer is a polyurethane, (R¹ is oxygen, R² is either analkyl group or an aryl group, and R³ is hydrogen), excision of thecarbonyl groups forms a surface containing a sufficient amount of aminegroups to impart antimicrobial activity.

Alternatively, the polymeric materials may be comprised of a polymerhaving the functional groups pendant to the polymer chain, rather thanin the polymer backbone. The polymeric materials may also be comprisedof copolymers and polymer blends of the above described polymers.

The resulting polymer species are not equally distributed throughout thematerials. Rather, selective irradiation of the material causes excisionof the carbonyl groups and the formation of the new polymer speciessubstantially on the material's surface. By the term "material'ssurface" it is meant the surface of the material and a depth extendingbelow the surface of less than about 1 micrometer (1 μm). A sufficientnumber of carbonyl groups are excised to impart antimicrobial activityto the surface of the material. This change in surface chemistry allowsthe material to inhibit microbial activity, whenever its surface comesinto sufficient contact with microorganisms. A sufficient amount ofcarbonyl groups may be excised by selective UV photon, high energyelectron, or low energy electron irradiation.

In a separate method, the surface of materials comprising an organicpolymer having repeating units of the structural formula, ##STR2##wherein, the polymer is selected from the group consisting of asynthetic or natural polyamide, polyurea, polyhydrazide, andpolyurethane may be rendered antimicrobial via chemical reduction.

Where the polymer is a synthetic polyamide, (R¹ is either an alkyl groupor an aryl group, R² is either an alkyl group or an aryl group, and R³is either hydrogen, an alkyl group or an aryl group), or a naturalpolyamide, (R¹ is R₄ --CH(NH), R² is an alkyl group, and R³ is hydrogen,an alkyl group, or an aryl group), chemical reduction forms a surfacecontaining a sufficient amount of amine groups to impart antimicrobialactivity. For the synthetic polyamide, R³ is preferably hydrogen,because the hydrogen bonding provides the polymer with higher thermalstability and mechanical properties. Where the polymer is a polyurea,(R¹ is NH, R³ is either an alkyl group or an aryl group, and R³ ishydrogen), chemical reduction forms a surface containing a sufficientamount of amine groups to impart antimicrobial activity.

Where the polymer is a polyhydrazide (R¹ is either an alkyl group or anaryl group, R² is NHC═O, and R³ is hydrogen), chemical reduction forms asurface containing a sufficient amount of hydrazine groups to impartantimicrobial activity.

Where the polymer is a polyurethane, (R¹ is oxygen, R² is either analkyl group or an aryl group, and R³ is hydrogen), chemical reductionforms a surface containing a sufficient amount of amine groups to impartantimicrobial activity.

Alternatively, the polymeric material may be comprised of a polymerhaving the functional groups pendant to the polymer chain rather than inthe polymer backbone. The polymeric materials may also be comprised ofcopolymers and polymer blends of the above-described polymers.

Effective reducing agents for chemically reducing the polymer to itscorresponding functional groups are known. Such agents are discussed inJerry March, Advanced Organic Chemistry. Reaction Mechanisms, andStructure (New York: John Wiley and Sons, 1985) and Ian T. Harrison andShuyen Harrison, Compendium of Organic Synthetic Methods (New York:Wiley-Interscience, 1971).

Polyamides, for example, may be rendered antimicrobial by chemicalreduction using a variety of reducing agents which are known to reduceamides to their corresponding amines in solution. These include, forexample, sodium borohydride in the presence of certain Lewis acids suchas aluminum chloride, cobalt (II) chloride (CoCl₂), or triethyloxoniumfluoroborate, lithium aluminum hydride (LiAlH₄), borane, andtrichlorosilane. These reagents may be used to reduce the amide groupslocated substantially on the surface of a polyamide material to aminegroups according to the reaction: ##STR3## wherein, R is H, an alkylgroup, or an aryl group,

R' is H or an alkyl group, and

R" is an alkyl group or an aryl group.

While the resulting product is not identical to that species formed byexcision of the carbonyl groups, the final result is the formation of asecondary or tertiary amine which renders the material's surfaceantimicrobial. If the amide groups are pendant to the polymer chain,rather than in the polymer backbone, a primary amine may also be formeddepending upon the degree of nitrogen substitution.

Reaction conditions should be chosen such that reduction occurs only atthe functional groups located at or near the surface of the polymericmaterial. For example, treatment of polyamide fibers using lithiumaluminum hydride in refluxing tetrahydrofuran (THF) was found to resultin significant loss in fiber weight. This may be due to excessivereduction of the amides over substantially the entire length of thepolymer molecules resulting in soluble polyamine species. When thereaction is carried out at room temperature, loss of fiber mass is notobserved.

The new polymer species formed by the above-described methods arechemically bound to the surface via the sub-surface portions of thepolymeric chains which have not been transformed by irradiation orreduction. Thus, the new polymer species do not leach into solutionswhich are contacted with the treated materials.

Suitable polymers for irradiation or reduction include, for example,synthetic polyamides such as poly(hexamethylene adipamide),poly(ε-caproamide), and poly(metaphenylene isophthalamide); naturalpolyamides such as wool, silk, and casein: polyureas, polyhydrazides,and polyurethanes.

The chemically reduced or irradiated material forms a new polymerspecies substantially on its surface which becomes progressively moreprotonated over a range of a pH of about 9 to a pH of about 5. At a pHof about 7, the polymer species are largely protonated, and at a pH ofabout 5, they are effectively all protonated. At a pH much above 9, thenew polymer species are not protonated, and thus are not effective asantimicrobial agents.

It has been found that in order to achieve the desired antimicrobialactivity by irradiation, the polymeric material must be in a form havinga specific surface area such that at least 0.02 m² /g and preferably atleast 0.20 m² /g of the material's surface area can be irradiated."Specific surface area" as used herein, can be determined by standardgas absorption techniques or, in the case of filamentary materials, bythe following formula: ##EQU1## wherein, p is the density of thepolymer(g/cm³) and Tex is the linear density of the individualfilaments(g/1000 m).

"Specific irradiated surface area" as used herein, refers to thespecific surface area times the fraction irradiated. It is theirradiated specific surface area of a unit quantity of material. Thefraction of the surface area irradiated for drawn fibers and stretchedfilms is determined by examining the surface of the material with ascanning electron microscope. Drawn fibers and stretched films, whenirradiated, exhibit characteristic features on the surface of thematerial such as transverse ridges as described in PCT application WO87/03021. The fraction of the specific surface area irradiated iscomputed by dividing the fraction containing these ridges by the totalsurface area. Undrawn yarns and unstretched films, when irradiated aresmooth and the specific irradiated surface area is inferred from themanner in which the material was irradiated. The specific irradiatedsurface area of the material approaches the specific surface area of thematerial when the form of the material is a card web or spunlacedfabric, a very open structure of low basis weight, and is a much smallerfraction, for example when the material is a fabric formed of a twistedyarn.

When the specific irradiated surface area of the material is less than0.20 m² /g, such as in most yarns, a relatively high level of energymust be imparted to the material to achieve the antimicrobial propertiesof the invention.

The materials used in the processes of this invention can be, forexample, in the shape of films, fibers, fibrids, powders, or articlesmade therefrom. A particularly preferred article is a spunlaced fabricproduced in accordance with the general procedures of Evans, U.S. Pat.No. 3,485,706, which is hereby incorporated by reference. Spunlacedfabrics generally have a suitable specific surface area for practicingthe processes of this invention and are in a convenient form to beirradiated to the required fraction of the specific surface area. Whenthe article is to be irradiated, woven and knit fabrics are lesspreferred, since high overlap among the fibers causes large portions ofthe article's surface to be shaded from the irradiation. For such anarticle, chemical reduction would be more effective.

In the present invention, one method for imparting antimicrobialactivity to the material by irradiation is through ultraviolet (UV)photons. The term "UV photons", as used herein, refers to photons havinga wavelength from 400 to 10 nm. Any source of photons can be employedthat generates light with the power and energy as described herein, andthat emits a wavelength that the article is capable of stronglyabsorbing as defined herein. Preferably, the UV photon wavelength is nogreater than 222 nm, and more preferably the wavelength is no greaterthan 193 nm. Suitable UV photon sources include, for example, Excimerlasers and ultraviolet (UV) lamps. Preferably, an ArF Excimer laserwhich generate wavelengths of 193 nm is used. ArCl lamps which generateswavelengths of 222 nm, ArF lamps which generate wavelengths of 193, andXe lamps which generate wavelengths of 172 nm may also be used. Thephoton source, particularly the UV lamp, is best operated in anon-absorbing, non-reactive gas or vacuum environment, e.g., not air.

It has been found that the material must be capable of stronglyabsorbing UV photon radiation. The phrase "the material must be capableof strongly absorbing" as used herein, is meant to include materialsthat directly absorb the UV photon energy.

Materials that strongly absorb UV photon radiation will generally absorbat least about 50% of the photon energy in about the first 20% of thethickness of the material or depending on the form, often about thefirst micrometer (1 μm) of the surface of the article being irradiated.The absorptivity at the wavelength of the UV photon radiation ismeasured in a spectrophotometer using a film of the material at a knownthickness.

The reduction in light intensity (I) from I_(o) to I is determined bythe following equation;

    I=I.sub.o *10-.sup.α* d

wherein,

d is the distance into the material.

Therefore, in order for at least 50% of the energy to be absorbed in thefirst 20% of the thickness of the material, α must be at least 1.5/Dwhere D is the thickness of the material (α*d must be at least 0.3 whend is 0.2,*D). Examples of strongly absorbing materials as definedherein, include a 1 denier per filament (dpf) (0.111 Tax) fiber with adiameter (thickness) of 11 micrometers having an α of at least 0.14reciprocal micrometers (μm⁻¹). A 1 mil film having a thickness of 25micrometers strongly absorbs UV photons when α is at least 0.06 μm⁻¹. A20 dpf (2.22 Tax) fiber having a thickness of 50 micrometers stronglyabsorbs UV photons when α is at least 0.03 μm⁻¹. However, a higherabsorbance of about 0.3 (μm⁻¹) is preferred. Specifically,poly(hexamethylene adipamide) fibers irradiated by photons having awavelength of 193 nm, strongly absorb photons with an α of 0.86 μm¹.When the photon wavelength is 248 nm, poly(hexamethylene adipamide)weakly absorbs photons with an α of 0.0096 μm⁻¹.

The material to be used in the present invention must be irradiated witha UV photon energy density of at least 300 mJ/cm². Energy densitiesbelow 300 mJ/cm² either produce no antimicrobial activity or do notproduce useful levels of antimicrobial activity. When the specificsurface area of the material is less than 0.2 m² /g, an energy densityof at least about 1.0 J/cm² should be employed. Further, it has beenfound that when the material is at least partially aromatic or whollyaromatic such as poly(metaphenylene isophthalamide), a UV photon energydensity of at least about 3 J/cm² should be employed to yield usefullevels of antimicrobial activity. Upper limits on photon energy aregoverned by a desire to reasonably maintain the material's structuralintegrity.

If an Excimer laser is used, the UV photon energy is generally impartedto the material at an irradiance of about 200 kw/cm², and more typicallyat 4 MW/cm² for 16 nanoseconds in order to achieve the antimicrobialactivity of this invention. If an ultraviolet (UV) lamp is used, the UVphoton energy is generally imparted to the material at an irradiance ofabout 1 W/cm² for 3,500 seconds.

Alternatively, electron irradiation may be used to impart antimicrobialactivity to the material. In electron irradiation, a flux of electronsimpinges on materials passing through an electron beam.

The extent to which the electrons impart antimicrobial activity to thematerial is a function of the number of electrons delivered per unit ofspecific surface area (dosage), and the probability that each electronwill cause the desired effect (cross-section). The cross-sectionincreases as the kinetic energy of the individual electrons decreases,until the energy falls below a critical minimum of about 6 electronvolts (eV). As a result, the required dosage of high energy electrons ismuch higher than the dosage needed for low energy electrons.

Furthermore, the depth of electron penetration is a function of theinitial kinetic energy of the electrons, i.e., electrons having lowerenergy have less penetration, and the composition of the material, i.e.,electrons more easily penetrate materials having a low average atomicnumber, such as organics. For organic materials, as described in C. A.Andersen and M. F. Hasler, "Extension of Electron MicroprobeTechniques," 4th International Congress of X-ray Optics andMicroanalysis, eds. R. Castaing, P. Deschamps, and J. Philibert (Paris:Hermann, 1966), pp. 310-327, the penetration of electrons having aninitial kinetic energy up to at least 50,000 eV increases approximatelyas the 1.68 power of energy. This relationship is defined in thefollowing formula, ##EQU2## wherein, Dp is the penetration depth inmicrometers,

(E) is the electron kinetic energy in thousands of electron volts (ev),and

p is the density in grams per cubic centimeter (g/cm³).

The term "irradiated volume" as used herein, is the product of theirradiated specific surface area by the penetration depth.

In the present invention, it is desirable to deposit the energy of theelectrons on the surface of the material in order that any chemicalchanges may occur substantially on the surface, and thus maintain thematerial's structural integrity. As more electrons penetrate thematerial, the likelihood of structural damage increases.

It is appreciated that this radiation-induced chemical reaction willproceed to the depth of electron energy penetration. However, for thepresent invention, it is important that the new polymer species formssubstantially on the surface of the material to impart usefulantimicrobial activity. Therefore, the depth of electron energypenetration is preferably less than about one micrometer (1 m). For athick section of a highly porous material, a sufficiently high electronenergy which penetrates the entire thickness is preferred.

In the present invention, an electron energy of at least 6.4 eV at anenergy absorption from the electrons of at least 10,000 erg/cm³ ofirradiated volume is required to impart antimicrobial activity to thesurface of the material. Preferably, the electron energy is no greaterthan 10,000,000 eV and the energy absorbed from the electrons is nogreater than 1,000,000 erg/cm³ of irradiated volume. More preferably,the electron energy is from 100 to 5000 eV, and the energy absorbed fromthe electrons is from 50,000 to 250,000 erg/cm³ of irradiated volume.

The present invention also provides processes for controllingmicroorganisms using the antimicrobial materials of the invention.Microorganisms can be controlled in a variety of media by contacting aneffective amount of the antimicrobial material with a microorganism. Aconvenient medium is an aqueous medium and a gaseous medium would behavesimilarly. Contacting the skin or other parts of a mammal with aneffective amount of the antimicrobial material would also be expected tocontrol microorganisms.

The antimicrobial material of the present invention controls a broadspectrum of microorganisms. The material has been found to be useful incontrolling bacteria, myceteae and viruses using the Shake Flask Testdescribed, infra. The antimicrobial material would also be expected tocontrol algae, protozoa, viroids and prions in a similar manner.

By the term "bacteria" is meant eubacteria and archaebacteria.Eubacteria include fermicutes, gracilicutes and ternicutes. Gracilicutesinclude gram-negative, facultatively anaerobic rods. Gram-negative,facultatively anaerobic rods include Enterobacteriaceae.Enterobacteriaceae include Klebsiella and Escherichia. Klebsiellainclude Klebsiella pneumniae and Escherichia include Escherichia coli.Fermicutes include the group gram-positive cocci, and the groupendospore-forming rods and cocci. Gram-positive cocci includeMicrococcaceae. Micrococcaceae include Staphylococcus and Staphylococcusincludes Staphylococcus aureus. Endospore-forming rods and cocci includeBacillaceae. Bacillaceae includes Bacillus which includes Bacilluscirculans. All references herein to bacteria are in accordance withBergey's Manual of Systematic Bacteriology, Williams & Wilkens, 1st ed.Vol. 1-4, (1984).

The term "Myceteae" includes Amastigomycota. Amastigomycota includeDeuteromycotina which includes Deuteromycetes. Deuteromycetes includeAspergillis and Candida. Aspergillis includes Aspergillis niger andCandida includes Candida albicans.

The term "virus" includes bacteriophage. Bacteriophage includes T-seriesbacteriophage which includes T-even bacteriophage such as bacteriophageT4.

Examples of suitable applications comprising the antimicrobial articlesand materials of the present invention include medical applications,dental devices, food wrap, floor coverings such as carpet backings, andcoatings. More specifically, examples of medical devices include woundclosure devices, such as those sutures which are generally described in"Gore-Tex" Suture Bulletins, W. L. Gore & Assoc., Inc. (1986). Examplesof devices for purifying or sterilizing aqueous solutions include thosewhich are generally described in Gelman Sciences Process MicrofiltrationCatalog, (April 1986). Similarly, examples of devices for purifying orsterilizing a gas include those which are generally described in"Nonwovens in Filtration (1987) Worldwide," Filter Media Consulting.Inc., (April 1988). Examples of catheters include those generallydescribed in "MEDSPEC 1989," Medical Devices Register, Inc., (1989).Examples of suitable devices for storing, transporting or dispensingsterile solutions, devices for controlling odors, wound dressings andgarments such as gowns and masks are generally described in "HospitalSupply Index," Product Analysis, Vol. 1A and 1D, IMS America Ltd.,(Third Quarter 1986). Examples of medical implants are generallydescribed in "The Orthopedic Implants and Allied Products MarketsOutside the U.S.," Frost & Sullivan, Inc., (April 1985). Examples offloor coverings, such as carpet backing, are generally described inEdwards, U.S. Pat. Nos. 3,563,838, Hendersen, 3,821,062 and Peterson,3,502,538. Examples of food wraps are generally described in Chemicalweek, Mar. 13, 1983, p. 11. Examples of coatings are generally describedin Biomedical Business International, Mar. 2, 1988, pp. 37-38 (Medical),Textil Praxis International, foreign edition with English supplement,1980, vol 35, pp. XVI-XXIII (Consumer), and West Marine ProductsCatalog, (P.O. Box 1020 Watsonville, Calif. 95077) (Summer 1989) pp.99-100 (Marine). Examples of tests in which a preservative comprisingthe antimicrobial material of the present invention could be used aredescribed in "United States Pharmacopeia, Microbiological Tests (51),"Antimicrobial Preservative Effectiveness, Vol XXII pp. 1478-1479 (1990).

Testing Methods

Antimicrobial activity was measured using the Shake Flask Test describedgenerally in U.S. Pat. No. 4,708,870 and outlined in Malek and Speier,The Journal of coated Fabrics, vol. 12, July 1982, pp. 38-45.

The Shake Flask Test requires the test material to be in a form having ahigh surface area to weight ratio. Furthermore, the surface area shouldbe predominantly treated so as to detect antimicrobial activity.Articles having the form of powders, fibers, and thin films have provento be acceptable. For instance, treating the surface of a polymer cubeweighing 0.75 g and then milling this into a powder prior to the ShakeFlask Test may not provide the necessary treated surface area to detectantimicrobial activity. However, treating the milled powder would beacceptable.

The bacterial inoculum for the Shake Flask Test was prepared bytransferring 2.0 ml of an overnight broth culture to a 300 mlnephyloculture flask (Bellco Glass Inc., Vineland, N.J.) containing 100ml of Tryptic Soy Broth (TSB) (Remel, Lexena, Kans.). This flask wasincubated at 373C with shaking (ca. 200 rpm). Growth of the culture wasdetermined during incubation using a Klett-Summerson photoelectriccolorimeter (Klett Mfg. Co., NY, N.Y.). When the culture reachedlate-log phase (185-200 Klett units for Klebsiella pneumonias ATCC4352), appropriate dilutions were made with sterile 0.2 mM phosphatebuffer (pH 7).

This inoculum was then placed into sterile, disposable 250 ml Erlenmeyerflasks (Corning Glass Co., Corning, N.Y.) containing 0.75 g of theMaterial produced by the process of this invention or a suitable controlmaterial as indicated below. Each flask contained a known concentrationof bacteria in a final volume of 75 ml phosphate buffer.

The initial concentration of bacteria used in the various examples wasdetermined by serial dilution of the inoculum (0.2 mM Phosphate buffer,pH 7) and plating in triplicate on Trypticase Soy Agar (TSA) plates(sold commercially by BBL, Cockeysville, Md.). The flasks were shaken ona Burrell wrist action shaker (Burrell Corp., Pittsburgh, Pa.). A 1.2 mlaliquot was removed from each flask after shaking for 1 hour (or otherappropriate time interval as indicated). Duplicate petri platescontaining TSA were inoculated via spread plating with 0.1 ml each ofthe sample. The remaining 1.0 ml was serial diluted and plated induplicate. The TSA plates were incubated at 373C. for 18 to 24 hours.Plates having between 30 and 300 colonies were counted and the bacterialconcentration determined from the mean of the plate counts. If none ofthe plates contained at least 30 colonies, all colonies were counted andthe bacterial concentration determined from the mean of the platecounts. Below the limit of detection of the procedure described herein,the colony count was said to be zero.

Alternately, microbial enumeration was performed using impedancetechniques via a Bactometer Model 123 Microbial Monitoring System. TwoBactometer wells containing Double Strength Plate Count Agar wereinoculated with 0.1 ml of sample from each flask. The modules wereincubated at 353C. and the impedence monitored. Densities of K.pneumoniae were calculated based upon comparing the sample impedencedetection time to an impedence vs. cfu/ml (colony forming units permilliliter) standard curve. Detailed description of this methodology isfound in R. Firstenberg-Eden, R. and G. Eden, Impedance Microbiology,(Letchworth, Hertfordshire, England: Research Studies Press Ltd., 1984),pp. 170.

When the Shake Flask test was conducted using Bacteriophage T4 forexamples 74 and 75, the titer was determined by plaque assay asdescribed in F. M. Ausubel et al., eds., Current Protocols in MolecularBiology, Section 3, Unit 1.11 (New York: John Wiley and Sons,Escherichia coli HB101 was used as the host.

Antimicrobial activity was determined by the formulas:

    k.sub.t =log10(C.sub.o)-log10(C.sub.t +1)

    D.sub.t =log10(CF.sub.t)-log10(C.sub.t +1)

where:

C_(o) =initial concentration of bacteria (cfu/ml) in test flask at timezero,

C_(t) =concentration of bacteria (cfu/ml) in test flask at time t (oneis added to the number to avoid calculating the log of zero),

CF_(t) =concentration of bacteria (cfu/ml) in control flask at time t,and

cfu/ml=colony forming units per milliliter.

The relationship between percent reduction and log reduction isconveniently seen by reference to the following:

    ______________________________________                                        % Reduction     Log Reduction                                                                             K.sub.t                                           ______________________________________                                        90              1           1                                                 99              2           2                                                 99.9            3           3                                                 99.99           4           4                                                 99.999          5           5                                                 ______________________________________                                    

In all the Examples, the organic polymer was tested substantially freeof fiber finish. In Examples 1-76, the finish was removed by knowntechniques such as washing with methanol and carbon tetrachloride eitherbefore or after irradiation. In Examples 77 to 115, the finish wasremoved as described, infra.

Laser irradiation for examples 1 to 76 was performed using Excimer lasermodels EMG 101MSC, EMG MSC or LPX 325iCC all manufactured by LambdaPhysik, Goettingen, Federal Republic of Germany. The laser containedstandard mixtures selected from the following gases: argon, fluorine,neon and helium. Light was emitted from the laser at a wavelength of 193nm and in pulses of about 16 nanoseconds. All irradiation was carriedout under ambient conditions.

High energy electron beam irradiation for examples 77 to 107 wasperformed using an electron beam accelerator, Model KS, available fromHigh Voltage Inc.

Low energy electron beam irradiation for examples 108 to 110 wasperformed using the following described apparatus.

The apparatus included a metal vacuum vessel having a pumping systemcapable of reducing pressure to 0.00002 torr (mm of Hg), a gauge formeasuring pressure, a door that could be opened to introduce and removesamples, and such additional, conventional features which are known tothose skilled in the art. These features are described in texts such asA. Roth, Vacuum Technology, 2nd ed. (New York: North-Holland PublishingCo., 1982), or in J. F. O'Hanlon, A Users Guide to Vacuum Technology,2nd ed. (New York: Wiley, 1989).

The apparatus also contained the following internal parts. A rotatableplaten which was driven by a motor controlled externally by an operator.The sample material to be treated was attached to the lower surface ofthe platen by "Kapton" tape and applied only to regions of the samplethat would be cut off after the treatment was complete. The platen waselectrically connected to the vessel. A filament assembly having threestrands of 0.01 inch diameter tungsten wire was connected in parallelbetween two insulated posts and positioned below the platen. The twoposts were insulated from the vacuum vessel and from each other. Thedistance between the posts was such that the length of the filamentassembly was approximately 3 inches. The height of the posts was suchthat the filament assembly was approximately 1.5 inches above the base.The base was metal and electrically isolated. The platen wasapproximately 4.75 inches above the filament assembly. The posts towhich the tungsten wires were attached were each connected electricallyto an individual terminal external to the vacuum vessel. The filamentassembly was located off-center with respect to the center of rotationof the platen such that the filament assembly's center was approximatelyat a horizontal distance of 2.5 inches from the center of the platen.The filament assembly was oriented such that the wires wereapproximately parallel to the radius of the platen above them. An 1.5inch diameter circle of stainless steel sheet having no protrusions onits front face, a current probe, was placed in various locations in thevessel and oriented such that the surface normal of the sheet pointedtowards the filament assembly. The current probe was electricallyisolated, except for being connected electrically to a terminal externalto the vacuum vessel.

The electrical connections of the apparatus were as follows. The vacuumvessel was connected to electrical ground. The beam power supply wasconnected so as to impress an adjustable voltage between the filamentassembly and the ground such that the filament assembly was negativewith respect to the ground. This voltage between the filament assemblyand the ground was the beam voltage. The current drawn from the beampower supply was the beam current. The current probe was connected tothe ground through a device to measure the current. This current flowingbetween the ground and the current probe was the probe current. A powersupply which was isolated from the ground was connected such that itcould impress a voltage between the two insulated posts that supportedthe filament assembly. This voltage was the filament power supply. Thecurrent drawn from the filament power supply was the filament currentand could be adjusted by the operator.

A sheet of the sample material to be treated was attached to the platenand the access to the vacuum vessel interior was closed. Valves to thepumps were opened and pumping continued until the pressure fell below0.00004 torr. The platen rotation motor controller was set to the speedchosen for the sample, typically 60 rpm. The filament power supply wasadjusted to obtain electron emission, typically 0.9 amperes. The beampower supply was adjusted to obtain the beam voltage chosen for theexperiment. The beginning of treatment was defined as the instant whenthe beam current flow began. Treatment continued for the specific timechosen for the sample. Treatment ended when the flow of beam current wasstopped. It will be appreciated that the rotation of the platen causedthe sample to move above the filament assembly so that a ring ofmaterial was thus exposed to the strongest irradiation. As soon as thetreatment was stopped, the flow of filament current was stopped and thefilament assembly was allowed to cool. Air was then let into the vacuumvessel and the access door was opened. The sample was then turned oversuch that the side which was previously against the platen now facedoutward. Care was taken to ensure that the center of the platen on thesample was at the same location after the sample was turned over. Thesecond side was subsequently treated in the same manner as the firstside.

X-Ray Photoelectron Spectroscopy (XPS)

X-ray Photoelectron Spectroscopy (XPS, also known as ESCA) is wellestablished as a means for obtaining elemental and chemical stateinformation from solid surfaces, including polymers. See for example"Practical Surface Analysis by Auger and X-ray PhotoelectronSpectroscopy", D. Briggs and M. P. Seah, eds., John Wiley & Sons, NewYork), 1983. Electrons are emitted and escape without energy loss from adepth of not less than a few nanometers below the solid surface. Thekinetic energy of these electrons is the difference between the energyof the x-rays which were used to eject and the energy binding them inthe orbitals of the atoms from which they came. Since the set of orbitalenergies is unique to each element, measuring the energy distribution ofthese emitted electrons provides a means of elemental analysis.Moreover, the orbital energies may shift by a small amount, typically afew electron volts or less, when the atoms are combined into chemicalcompounds, the "chemical shift".

Thus the x-ray photoelectron spectrum of 6/6 nylon shows electrons atenergies corresponding to carbon, nitrogen and oxygen. Looking moreclosely in the energy range for electrons emitted from the 1s orbital ofcarbon (C 1s peak), two groups separated by about 3 eV are seen. It isknown that the more numerous lower binding energy group corresponds tocarbon in aliphatic bonds, while that of the higher energy groupcorresponds to carbon in a carbonyl environment.

The surface analysis for the Examples was performed using an Escalab-2surface analysis instrument available from VG Instruments, Inc.,Danvers, Mass. The instrument was operated according to the ordinarypractice for such instruments as described in the operator's manualsupplied by the vendor. For X-Ray Photoelectron Spectroscopy (XPS), themagnesium anode was used with the power supply set to supply a currentof 20 milliamperes at 15,000 volts. The electron energy analyzer iriswas set to 14, the aperture to 3 mm, and the pass energy to 50 eV. In afew cases, a large enough sample was available to use a 15 mm×6 mmaperture instead of the 3 mm aperture, and thus collect data at a fasterrate. Samples were placed into the instrument by attaching them to oneof the sample stubs supplied with the instrument. The stubs provided aflat, horizontal surface, about 10 mm in diameter, to which the sampleswere attached.

To analyze a fabric, a sample, about 1×2 cm was cut from the fabric andwashed with fresh, reagent grade trichlorotrifluoroethane, knowncommonly as "Freon" TF, purchased from Miller-Stephenson Co. Inc. ofDanbury Conn. as type MS-182. After washing, the sample was handled onlywith similarly cleaned tweezers. Two pieces of fabric, each being atleast 5×5 mm, but small enough not to extend beyond the perimeter of thestub, were cut from the washed sample of fabric and set one on top ofthe other on the sample holding stub of the surface analysis instrument.A square of common aluminum foil, about 15×15 mm, was cut and a hole,about 4 mm in diameter, was punched through it, approximately at thecenter. The aluminum foil was then washed and handled subsequently inthe same manner as the fabric sample. The aluminum foil was placed overthe fabric pieces on the stub so that the hole in the foil was more orless at the center of the stub and the fabric was visible through it.The edges of the foil were crimped down over the top of the stub inorder to hold the fabric pieces in place. The fabric pieces were thenput into the surface analysis instrument.

The standard data collection practice consisted of a survey scanextending in binding energy from 25 electron volts to 1125 electronvolts in steps of 0.7 eV, counting for 200 milliseconds at each step.The purpose of the survey scan was to detect the presence of anyunanticipated contaminants. Spectra were also collected from theneighborhood of the 1s peaks of carbon, oxygen and nitrogen. Thesespectra went from about 5 eV below the expected peak position to about10 eV above it, in steps of 0.1 eV. Data was collected. Typically 1000,8000, and 4000 milliseconds per data point were used for carbon,nitrogen and oxygen, respectively. These times were adjusted tocompensate for variations in concentration, or to provide still betterdata quality when it was needed for more demanding forms of dataanalysis.

The data was analyzed using the computer programs supplied with theinstrument by the vendor in the manner described in the vendor'smanuals. Applying these programs to the data from the carbon, nitrogenand oxygen 1s peaks gave the elemental composition of surface in termsof the atom percent of each element. The carbon 1s peak was furtheranalyzed to quantitatively determine the relative amounts of individualcontributions, especially carbonyl. The assignments of contributionswere made according to accepted values appearing in the scientificliterature. The separation of the peak into contributions wasaccomplished by means of the computer programs supplied by the vendorwith the instrument used in the manner set forth in the vendor'smanuals.

Four samples of untreated poly(hexamethylene adipamide) fabric:(poly(hexamethylene adipamide) fibers sold commercially by E. I. du Pontde Nemours and Company as type 200SD having a dpf of 1.8 (0.2 Tex) werespunlaced to yield a fabric) were analyzed in the foregoing manner. Theresults are shown in Table A.

                  TABLE A                                                         ______________________________________                                        Test Number                                                                             Carbon   Nitrogen  Oxygen  Carbonyl                                 ______________________________________                                         83       79.545    9.169    11.286  13                                        85       78.535    9.928    11.537  14                                       223       78.710   10.037    11.252  14                                       227       79.107   10.627    10.266  14                                       ______________________________________                                    

The values for carbon, nitrogen and oxygen are in atom percent. Thevalue for carbonyl is the percent of the total carbon 1s peak thatarises from carbon in a carbonyl environment. The agreement between thecarbonyl content and the carbon/oxygen ratio indicates that essentiallyall the oxygen in the polymer is present as the carbonyl.

Four samples of poly(hexamethylene adipamide) fabric:(poly(hexamethylene adipamide) fibers sold commercially by E. I. du Pontde Nemours and Company as type 200SD having a dpf of 1.8 (0.2 Tex) werespunlaced to yield a fabric) irradiated by a laser in a similar manneras described in Table I, Radiation Treatment A4, infra, were alsoexamined. The results are shown in Table B.

                  TABLE B                                                         ______________________________________                                        Test No.  Carbon   Nitrogen  Oxygen  Carbonyl                                 ______________________________________                                         81       79.540   8.787     11.674  12                                        79       80.165   8.924     10.911  10                                       103       79.100   8.675     12.224   8                                       109       80.951   8.961     10.089   8                                       ______________________________________                                    

From Table B it is seen that about 25% to about 50% of the carbonylgroups have been removed. The values for the carbon, nitrogen, andoxygen are atom percent, and carbonyl is the percent of the total carbon1s peak that arises from carbon in a carbonyl environment. It is notedthat the carbonyl contribution has decreased for the irradiated samples.The significance of this decrease is made clearer by noticing that ifhalf the carbonyl groups were excised, the carbonyl fraction for theirradiated samples would be half the value of the carbonyl fraction forthe unirradiated samples, i.e, decreasing from about 14 to about 7. Itis also noted that in the irradiated samples, there is more oxygen thancan be accounted for by the carbonyl groups, indicating that otheroxygen species are present. The differences among the irradiated samplescan be attributed to the irradiation procedures which do not assureprecisely the same photon dose to each and every location on the fabricsurface.

The following designations are referred to in the Examples below:

1. IC; Designates "Inoculated Control" and refers to a flask containingbuffer and bacteria alone.

2. UC; Designates "Uninoculated Control" and refers to a flaskcontaining buffer alone.

3. PC; Designates "Positive Control" and refers to poly(ethyleneterephthalate) yarn treated with 0.15% by weight of a 72% by weight inmethanol solution of the antimicrobial agent 3(trimethoxysilyl)propyloctadecyldimethyl ammonium chloride. The antimicrobial agent issold commercially by Dow Chemical Co. Midland, Mich. as DC-5772. Theyarn treated with DC-5772 is sold commercially by E. I. du Pont deNemours and Company as type D212 Dacron^(R) yarn. The yarn has a denierper filament of 28.0 and a specific surface area of 0.054 m² /g.

4. NC; Designates "Negative Control" and refers to poly(ethyleneterephthalate) yarn having a denier per filament of 28.0 and a specificsurface area of 0.054 m² /g. The yarn is sold commercially by E. I. duPont de Nemours and Company as type D692 "Dacron" yarn.

LASER IRRADIATED EXAMPLE 8 SPUNLACED FABRIC EXAMPLES

Irradiation Conditions

A variety of organic polymeric materials were spunlaced according to thegeneral procedure of Evans U.S. Pat. No. 3,485,706. The spunlacedfabrics were irradiated by placing 1 m² samples on a drum roller havinga 1 m circumference. Exposure of the sample to the light beam wascontrolled by rate of drum rotation and lateral movement of the drum.The fabric was turned over to expose the back of the spunlaced fabric tothe laser light and the process of irradiation repeated. Greater than90% of the specific surface area of the spunlaced fabrics wereirradiated as determined by scanning electron microscope.

For all spunlaced fabrics, an Excimer laser model EMG 202MSC wasoperated at 100 Hz with an energy output of 150 mJ/pulse. The beam areafor treatment A shown in Table I was 1.76 cm². The beam area was reducedfor radiation treatments B, C, D and E using a MgFl₂ cylindrical lenswith a focal length of 256 mm at a wavelength of 193 nm.

For all spunlaced examples shown in Tables II and III, the drum wasrotated at 24 rpm. Lateral speed of the drum passing in front of thelaser was varied as shown in Table I to result in 50% circumferentialand 50% lateral overlap of beam area, so that any one point on each sideof the fabric was exposed to 4 pulses of light in one pass of the drumin front of the beam.

Irradiation conditions for spunlaced fabric examples are detailed inTable I. As an illustration, radiation treatment A1 results in greaterthan 90% of the specific surface area of the fabric receiving 0.34 J/cm²in one pass.

                                      TABLE I                                     __________________________________________________________________________    Irradiation Conditions for Spunlaced Fabrics                                           Lens Lateral        Energy/                                                                              Total                                     Radiation                                                                              Distance                                                                           speed                                                                              Irradiance                                                                              Pulse  Energy                                    Treatment                                                                           Lens                                                                             (mm) (cm/min)                                                                           Passes                                                                            (MW/cm.sup.2)                                                                       (mJ/cm.sup.2)                                                                        (J/                                       __________________________________________________________________________    A1    NO NA   26.4 1    5.3   85    0.3                                       A2    NO NA   26.4 2    5.3   85    0.6                                       A3    NO NA   26.4 4    5.3   85    1.3                                       A4    NO NA   26.4 8    5.3   85    2.7                                       A5    NO NA   26.4 16   5.3   85    5.4                                       A6    NO NA   26.4 32   5.3   85    10.9                                      B1    YES                                                                              128  13.2 1   10.6  170    0.6                                       B2    YES                                                                              128  13.2 2   10.6  170    1.3                                       B3    YES                                                                              128  13.2 4   10.6  170    2.7                                       B4    YES                                                                              128  13.2 8   10.6  170    5.4                                       B5    YES                                                                              128  13.2 16  10.6  170    10.9                                      C1    YES                                                                              191   6.6 1   21.0  340    1.36                                      C2    YES                                                                              191   6.6 2   21.0  340    2.72                                      C3    YES                                                                              191   6.6 4   21.0  340    5.44                                      C4    YES                                                                              191   6.6 8   21.0  340    10.90                                     D1    YES                                                                              223   3.3 1   43.0  680    2.72                                      D2    YES                                                                              223   3.3 2   43.0  680    5.44                                      D3    YES                                                                              223   3.3 4   43.0  680    10.90                                     E1    YES                                                                              239   1.7 1   85.0  1360   5.44                                      E2    YES                                                                              239   1.7 2   85.0  1360   10.9                                      __________________________________________________________________________

Spunlaced Poly(hexamethylene adipamide) fabric: Poly(hexamethyleneadipamide) fibers sold commercially by E. I. du Pont de Nemours andCompany as type 200SD having a dpf of 1.8 (0.2 Tex) were spunlaced toyield a fabric with a basis weight of 44 g/m². The spunlaced fabric hada specific surface area of 0.235 m² /g.

Irradiated poly(hexamethylene adipamide) spunlaced fabric demonstratedantimicrobial activity as determined by the Shake Flask Test. In allcases except for Example 2, after 1 hour exposure to irradiatedpoly(hexamethylene adipamide) fabric, the population of Klebsiellapneumoniae was reduced by greater than 99%. Complete reduction wasevident in poly(hexamethylene adipamide) spunlaced fabric examplesirradiated with as little energy as 1.36 J/cm². By 24 hours, allirradiated poly(hexamethylene adipamide) examples reduced the bacterialpopulation below the limit of detection.

Results are detailed in Table II.

                  TABLE II                                                        ______________________________________                                        Antimicrobial Activity Associated with Irradiated                             Spunlaced Poly(hexamethylene adipamide)                                       Ex-                                                                           am-  Radiation Initial*  1 Hour                                               ple  Treatment cfu/ml    cfu/ml  k.sub.t                                                                              D.sub.t                               ______________________________________                                         1   None      1.50E+05  1.51E+05                                                                              0.00   0.00                                   2   A1        1.50E+05  1.87E+03                                                                              1.90   1.90                                   3   A2        1.50E+05  7.50E+00                                                                              4.30   4.30                                   4   A3        1.50E+05  2.50E+00                                                                              4.78   4.78                                   5   A4        1.50E+05  0.00E+00                                                                              5.18   5.18                                   6   A5        1.50E+05  2.50E+00                                                                              4.78   4.78                                   7   A6        1.50E+05  0.00E+00                                                                              5.18   5.18                                   8   B1        1.50E+05  3.38E+02                                                                              2.65   2.65                                   9   B2        1.50E+05  0.00E+00                                                                              5.18   5.18                                  10   B3        1.50E+05  0.00E+00                                                                              5.18   5.18                                  11   B4        1.50E+05  0.00E+00                                                                              5.18   5.18                                  12   1B5       1.50E+05  2.50E+00                                                                              4.78   4.78                                  13   C1        1.50E+05  6.00E+01                                                                              3.40   3.40                                  14   C2        1.50E+05  5.00E+00                                                                              4.48   4.48                                  15   C3        1.50E+05  7.50E+00                                                                              4.30   4.30                                  16   C4        1.50E+05  0.00E+00                                                                              5.18   5.18                                  17   D1        1.50E+05  2.75E+01                                                                              3.74   3.74                                  18   D2        1.50E+05  0.00E+00                                                                              5.18   5.18                                  19   D3        1.50E+05  0.00E+00                                                                              5.18   5.18                                  20   E1        1.50E+05  1.25E+01                                                                              4.10   4.10                                  21   E2        1.50E+05  4.00E+01                                                                              3.57   3.57                                  NC   None      1.50E+05  1.89E+05                                                                              0.00   0.00                                  PC   None      1.50E+05  7.50E+00                                                                              4.30   4.40                                  IC   None      1.50E+05  1.90E+05                                                                              -0.10  -0.10                                 UC   None      0.00E+00  0.00E+00                                                                              NA     NA                                    ______________________________________                                         * K. pneumoniae                                                               1.50E+05 = 150,000 cfu/ml.                                               

Spunlaced fabric of poly(metaphenylene isophthalamide) fibers (1.5 dpf)sold commercially as "Sontara" style E-88 by E. I. du Pont de Nemoursand Company were irradiated in the following examples. The fabric had abasis weight of 31 g/m² and a specific surface area of 0.234 m^(2/) g.

Poly(metaphenylene isophthalamide) spunlaced fabric was irradiated at anenergy of 10.9 J/cm² as detailed in the Radiation Conditions describedin Table I. These examples did not evidence significant antimicrobialactivity in 1 hour exposure to initial Klebsiella populations of1.05E+03 to 1.05E+05 cfu/ml. After 24 hour exposure to irradiatedsamples, antimicrobial activity was evidenced in most examples as shownin Table III.

                  TABLE III                                                       ______________________________________                                        Antimicrobial Activity Associated with                                        Poly(metaphenylene isophthalamide)                                            Spunlaced Fabric Irradiated                                                   with 10.9 J/cm.sup.2                                                          Radiation    Initial*  1 Hour                                                 Example                                                                              Treatment cfu/ml    cfu/ml  k.sub.t                                                                             D.sub.t                              ______________________________________                                        IC     None      1.05E+04  5.98E+03                                                                              0.25  -0.41                                IC     None      1.05E+05  6.45E+04                                                                              0.36  -0.46                                UC     None      0.00E+00  0.00E+00                                                                              NA    NA                                   22     A6        1.05E+03  0.00E+00                                                                              3.02  1.70                                 23     B5        1.05E+03  5.00E+00                                                                              2.24  0.92                                 24     C4        1.05E+03  2.35E+02                                                                              0.67  -0.65                                25     D3        1.05E+03  1.09E+03                                                                              0.20  1.12                                 26     E2        1.05E+03  3.00E+03                                                                              -0.46 -1.78                                27     A6        1.05E+04  5.00E+01                                                                              2.45  1.79                                 28     B5        1.05E+04  2.50E+00                                                                              3.63  2.97                                 29     C4        1.05E+04  1.46E+03                                                                              1.52  0.86                                 30     D3        1.05E+04  2.25E+04                                                                              -0.32 -0.99                                31     E2        1.05E+04  3.00E+04                                                                              -0.46 -1.12                                32     A6        1.05E+05  2.50E+00                                                                              4.63  3.81                                 33     B5        1.05E+05  2.50E+00                                                                              4.63  3.81                                 34     C4        1.05E+05  2.38E+03                                                                              1.88  1.06                                 35     D3        1.05E+05  5.27E+04                                                                              0.52  -0.31                                36     E2        1.05E+05  3.00E+05                                                                              -0.46 -1.28                                37     None      1.05E+03  5.00E+00                                                                              1.32  -0.01                                38     None      1.05E+04  2.27E+03                                                                              0.83  0.16                                 39     None      1.05E+05  1.58E+04                                                                              0.85  0.03                                 NC     None      1.05E+03  1.28E+02                                                                              2.87  0.08                                 PC     None      1.05E+03  0.00E+00                                                                              4.90  2.11                                 ______________________________________                                         * K. pneumoniae                                                          

YARN EXAMPLES

Poly(hexamethylene adipamide) yarn (sold commercially by E. I. du Pontde Nemours and Company and designated 200-34-R35 Type 496 nylon yarn)having a denier per filament of 5.9 and a specific surface area of 0.130m^(2/) g was irradiated in accordance with the process of the invention.The yarn was drawn about 3.5×in the course of its manufacture. Resultsare detailed in Table IV.

To irradiate the yarn, the untwisted yarn was spread so that most of itssurface area was irradiated as determined by scanning electronmicroscope. The 34-filament yarn was spread into a double layer offilaments by first passing the yarn through a standard three rolltensioning device, adding enough tension (40 to 50 g), and then wrappingit 4.5 turns around a pair of air-bearing rolls, slightly canted toadvance the yarn. Each wrap was advanced about 1 mm from the precedingwrap with 5 turns on the laser side and 4 behind. Thus, the yarn, spreadinto a ribbon, was passed at 1.10 meters per second directly in front ofthe laser beam positioned between the pair of air bearing rolls. All 4.5wraps were in the 1.76 cm² beam area. The beam impinged directly on oneside of the ribbon during the 5 turns on the laser side and on theopposite side of the ribbon during the 4 turns on the back side. A 193nm mirror was mounted behind the yarn in the laser beam path to reflectthe energy back to the spread yarn. Under these conditions,approximately 50% of the energy was returned from the mirror. The yarnwas wound on a bobbin after being irradiated. After a pass, the ribbonwas collapsed by unwinding under low tension using a rolling take offand was reformed with a different array on each succeeding pass. Theprocedure was repeated for a total of 20 passes.

An Excimer laser model EMG 202MSC was operated without a lens at 100 Hz,150 mJ/pulse and at an average power of 15W so that the energy per passwas 0.6 J/cm². The irradiance was about 5.3 MW/cm². It is inherent inmultiple pass processes that some areas receive greater energy thanothers, so the total energy represents an average. It can be noted thatfor each pass, about 50% of the specific surface area of the yarn wasexposed to both the direct and reflected laser radiation. After 5passes, specific surface area exposure increased to nearly 100%.

Antimicrobial activity of the yarn as determined by the Shake Flask Testdemonstrates a greater than 4 log kill in one hour as shown in Table IV.

                  TABLE IV                                                        ______________________________________                                        Antimicrobial Activity Associated with                                        Poly(hexamethylene adipamide) Yarn Irradiated                                 with 12 J/cm.sup.2 Energy                                                            Radiation  1 Hour                                                      Example                                                                              Treatment  cfu/ml     k.sub.t D.sub.t                                  ______________________________________                                        IC     None       3.31E+04   0.01    0.16                                     NC     None       2.03E+04   0.23    0.00                                     PC     None       0.00E+00   4.53    4.31                                     40     None       4.68E+04   -0.14   0.01                                     41     None       4.95E+04   -0.16   -0.01                                    42     12 J/cm.sup.2                                                                            0.00E+00   4.53    4.68                                     43     12 J/cm.sup.2                                                                            0.00E+00   4.53    4.68                                     ______________________________________                                         Initial concentration K. pneumoniae = 3.41E+04 cfu/ml                    

Undrawn poly(hexamethylene adipamide) yarn was prepared by spinningflake into a 51 filament yarn having a total bundle denier of 200. Theyarn had a specific surface area of 0.159 m² /g, a relative viscosity of48.5 and 44 equivalents of amine ends per 10⁶ g.

The yarn was wound on the drum roller used in the spunlaced fabricexamples described above. Prior to winding the yarn on the drum, a stripof tape was placed axially on the drum. The yarn was irradiated on thedrum with an Excimer laser LPX 325iCC operating without a lens at 250 Hzand 200 mJ/pulse. The drum was rotated at 30.3 RPM and with a lateralspeed of 0.0254 m/min. This resulted in each unit area of the yarn beingirradiated with 180 pulses of 67 mJ/cm² each for a total energy of 12.0J/cm². The irradiance was about 4.2 MW/cm². After one side had beenirradiated, a second strip of tape was placed on it in the same locationas the first strip of tape. The yarn was then cut off the drum byslitting along the middle of the taped portion. The warp was then turnedover, placed back on the drum and irradiated on the other side. Thefraction of surface area irradiated could not be ascertained directlysince fibers having very low orientation do not develop thecharacteristic surface structures during irradiation. However by analogywith Examples 46 and 47, greater than half of the specific surface areawas irradiated. After one hour exposure to the material as seen inExample 45, Table V, the bacterial population was reduced below thelimit of detection.

                  TABLE V                                                         ______________________________________                                        Antimicrobial Activity Associated with                                        Undrawn Poly(hexamethylene adipamide) Yarn                                           Radiation  1 Hour                                                      Example                                                                              Treatment  cfu/ml     k.sub.t D.sub.t                                  ______________________________________                                        44     None       1.85E+04   0.28    0.00                                     45     12 j/cm.sup.2                                                                            0.00E+00   3.54    3.27                                     IC     None       1.10E+05   -0.49   -0.77                                    UC     None       0.00E+00   NA      NA                                       ______________________________________                                         Initial concentration K. pneumoniae = 3.5E+04 cfu/ml                     

Poly(ε-caproamide) yarn (sold commercially by Allied Signal Corp. as40-12 denier 100% Type-6 nylon yarn was irradiated as described abovefor Examples 44 and 45 with 12.0 J/cm². The specific surface area ofthis 3.3 dpf yarn was 0.173 m² /g. Scanning electron photomicrographsindicated that greater than 50% of the surface area had been irradiated.

                  TABLE VI                                                        ______________________________________                                        Antimicrobial Activity Associated with                                        Irradiated poly(ε-caproamide) Yarn                                              Radiation  1 Hour                                                   Example   Treatment  cfu/ml    k.sub.t                                                                            D.sub.t                                   ______________________________________                                        46        None       5.2E+04   0.22 0.00                                      47        12 J/cm.sup.2                                                                            0.0E+00   4.93 4.72                                      IC        None       8.1E+04   0.03 -0.19                                     UC        None       0.0E+00   NA   NA                                        ______________________________________                                         Initial Concentration K. pneumoniae = 8.6E+04 cfu/ml                     

Poly(hexamethylene adipamide) yarn modified with 2.4% by weight ofN,N'-bis(3-aminopropyl)piperazine (APP) by stoichiometrically replacinga portion of the hexamethylene diamine monomer with (APP)(soldcommercially by E. I. du Pont de Nemours and Company as 100-34-R25 Type181B deep-dye automotive yarn) was irradiated on the drum winder asdescribed above for Examples 44 and 45 with an energy of 12.0 J/cm². Thedrawn yarn has a relative viscosity of 40 and 112 total titratable amineends per 10⁶ g. This yarn has a specific surface area of 0.184 m² /g.Greater than 50% of the specific surface area of the yarn was irradiatedas determined by scanning electron microscope. Antimicrobial activity isshown in Table VII.

Undrawn Poly(hexamethylene adipamide) yarn modified with 2.4% by weightof N,N'-bis(3-aminopropyl)piperazine:

The flake used in producing the yarn of Examples 50 and was spun on asmall spinning unit into a 200 denier undrawn yarn having 51 filaments.The yarn had a relative viscosity of 31, 130 equivalents of titratableamine ends per 10⁶ g and a specific surface area of 0.159 m² /g. Theyarn was irradiated on the drum winder as described above for Examples44 and 45 with an energy of 12.0 J/cm². Greater than 50% of the specificsurface area of the yarn was irradiated by analogy with Examples and 51.Antimicrobial activity is shown in Table VII.

                  TABLE VII                                                       ______________________________________                                        Antimicrobial Activity Associated with                                        Irradiated Poly(hexamethylene adipamide)                                      modified with 2.4% by weight of                                               N,N'-bis(3-aminopropyl)-piperazine                                                      Radiation                                                                             1 Hour                                                      Example                                                                              Material Treatment cfu/ml k.sub.t                                                                              DT                                    ______________________________________                                        48     Undrawn  12 J/cm.sup.2                                                                           2.5E+00                                                                              4.44   4.09                                  49     Undrawn  None      3.1E+04                                                                              0.35   0.00                                  50     Drawn    12 J/cm.sup.2                                                                           0.0E+00                                                                              4.84   4.78                                  51     Drawn    None      6.0E+04                                                                              0.06   0.00                                  IC     --       None      7.4E+04                                                                              -0.03  -0.21                                 UC     --       None      0.0E+00                                                                              NA     NA                                    ______________________________________                                         Initial concentration K. pneumoniae = 6.9E+04 cfu/ml                     

KNIT AND WOVEN FABRIC EXAMPLES

Knit fabric of poly(hexamethylene adipamide) monofilament soldcommercially as 15-1 denier type 280 nylon 66 by E. I. du Pont deNemours and Company was irradiated. The tricot knit fabric had thefollowing characteristics:

Specific surface area =0.08 m² /g

Wales=46 ends

Courses=43 ends

Thickness=0.007 BSI British standard units

Specific volume (bulk)=5.41

Fabric weight=0.97 oz/yd²

The fabric was placed on the drumroller used for the spunlaced fabricexamples. The drum roller rotated at 30 rpm with a lateral speed of 0.45m/min. An Excimer laser model LPX 325iCC was operated at 250 Hz and 200mJ/pulse resulting in each area receiving 10 pulses or 0.67 J/cm² /pass.The irradiance was about 4.2 MW/cm². Greater than 40% of the surfacearea of the fabric was irradiated. Results are shown in Table VIII.

Plain Woven fabric of poly(hexamethylene adipamide) of 40-34 denierfiber sold commercially as Type 285 SD nylon 66 by E. I. du Pont deNemours and Company were irradiated. The woven fabric had the followingcharacteristics:

Specific surface area=0.290 m² /g

Warp=178 ends/inch

Thickness=0.004 inches (ASTM)

Weight=1.61 oz/yd²

Specific volume (bulk)=1.86

Fill=112 ends/inch

The fabric was irradiated as described for the knit fabric Examples 58to 63. Less than 6% (less than 0.02 m² /g) of the surface area of thefabric was irradiated.

Spunlaced fabric of poly(hexamethylene adipamide) prepared as describedfor Examples 1 to 21

                                      TABLE VIII                                  __________________________________________________________________________    Antimicrobial Activity Associated with Laser Irradiated Knit and              Woven fabrics of poly(hexamethylene adipamide)                                Material   Passes                                                                             J/cm.sup.2                                                                         1 Hour       24 Hour                                     Example                                                                            Type  Per Side                                                                           per side                                                                           cfu/ml                                                                             k.sub.t                                                                          Δ.sub.t                                                                      cfu/ml                                                                             k.sub.t                                                                            Δ.sub.t                     __________________________________________________________________________    52   Woven 0    0.00 6.5E+04                                                                            0.00                                                                             0.00 2.05E+05                                                                           -0.50                                                                              0.00                              53   Woven 1    0.64 4.8E+04                                                                            0.13                                                                             0.13 1.04E+05                                                                           -0.20                                                                              0.29                              54   Woven 2    1.32 4.6E+04                                                                            0.15                                                                             0.15 8.15E+04                                                                           -0.10                                                                              0.40                              55   Woven 4    2.64 5.4E+04                                                                            0.08                                                                             0.08 2.30E+05                                                                           -0.55                                                                              -0.05                             56   Woven 8    5.28 5.9E+04                                                                            0.04                                                                             0.04 1.45E+05                                                                           -0.35                                                                              0.15                              57   Woven 16   10.56                                                                              2.5E+04                                                                            0.41                                                                             0.41 3.10E+02                                                                           2.32 2.82                              58   Knit  0    0.00 5.7E+04                                                                            0.06                                                                             0.00 1.95E+05                                                                           -0.48                                                                              0.00                              59   Knit  1    0.66 9.SE+01                                                                            2.82                                                                             2.76 0.00E+00                                                                           4.11 4.59                              60   Knit  2    1.32 2.5E+00                                                                            4.41                                                                             4.36 0.00E+00                                                                           4.81 5.29                              61   Knit  4    2.64 5.0E+00                                                                            4.11                                                                             4.06 0.009+00                                                                           4.81 5.29                              62   Knit  8    5.20 1.0E+01                                                                            3.81                                                                             3.76 0.00E+00                                                                           4.81 5.29                              63   Knit  16   10.56                                                                              0.0E+00                                                                            4.81                                                                             4.76 0.00E+00                                                                           4.81 5.29                              64   Spunlaced                                                                           0    0.00 5.9E+04                                                                            0.04                                                                             0.00 8.959+05                                                                           -1.14                                                                              0.00                              65   Spunlaced                                                                           4    10.64                                                                              7.5E+00                                                                            3.94                                                                             3.90 0.00E+00                                                                           4.01 5.93                              IC         NA   NA   6.5E+04                                                                            0.00                                                                             -0.03                                                                              1.05E+05                                                                           -0.21                                                                              -0.24                             UC         NA   NA   0.0E+00                                                                            NA NA   0.00E+00                                                                           NA   NA                                __________________________________________________________________________     Initial Concentration = 6.5E+04 cfu/ml, K. pneumoniae                    

was used as a control for Example 64. The irradiated spunlaced fabric ofExample 65 was irradiated according to Radiation Treatment A4 as setforth in Table I.

As shown in Table VIII, after 24 hours exposure to irradiated wovenfabric antimicrobial activity was evident only in Example 57 which wasexposed to a very high level of radiation.

After 1 hour exposure to irradiated knit fabric, the population of K.pneumoniae was reduced by greater than 99%. Complete reduction wasevident in knit fabric Examples 59 to 63 by 24 hours.

BROAD SPECTRUM ACTIVITY EXAMPLES

To illustrate the broad spectrum activity of the material produced bythe process of this invention, the Shake Flask Test as described hereinwas conducted replacing K. pneumoniae with a variety of othermicroorganisms.

Antimicrobial activity associated with laser irradiatedpoly(hexamethylene adipamide) materials produced by the process of theinvention have a broad activity as evidenced by the ability to reducepopulations of Aspergillus niger (Table IX), Candida albicans (Table X),spores of Bacillus circulans (Table XI) and Bacteriophage T4 (TableXII), Staphylococcus aureus (Example 74) and Escherichia coli (Example75).

For Examples 66 to 75, irradiated poly(hexamethylene adipamide)spunlaced fabric and yarn were employed in the Shake Flask Test. Thespunlaced fabric used as controls in the Shake Flask Test of Examples66, 68, 70 and 72 was the same type of spunlaced fabric described aboveand employed in Example 1. The spunlaced fabric in the Shake Flask Testof Examples 67, 69, 71, 73, 74 and 75 was irradiated as described forExamples 1 to 21, except that an Excimer laser model LPX 325iCC wasoperated without a lens at 250 Hz and 200mJ/pulse and each side wasexposed to 4 to 6 passes of the laser for a total energy as indicated.The irradiance was about 4.2 MW/cm², The drum was operated at 30 rpm andthe lateral speed of the drum was 17.7 inches/minute. The yarn used inthe Shake Flask Test of Example 73 was irradiated as described above forExamples 42 and 43. The yarn used in Example 74 was the same yarnemployed in Examples 40 and 41.

                  TABLE IX                                                        ______________________________________                                        Activity of Irradiated Spunlaced Fabric                                       of Poly(hexamethylene adipamide)                                              to Aspergillis niger.                                                         Radiation       1 Hour                                                        Example Treatment   pg/ml     k.sub.t                                                                              D.sub.t                                  ______________________________________                                        66      None        4.3E+04   0.37   0.00                                     67      3.33 J/cm.sup.2 /side                                                                     2.2E+02   2.66   2.29                                     IC      None        1.4E+05   -0.15  -0.51                                    UC      None        0.0E+00   NA     NA                                       ______________________________________                                         Initial Concentration A. niger = 1.0E+05 propagules/ml (pg/ml)           

                  TABLE X                                                         ______________________________________                                        Activity of Irradiated Spunlaced Fabric                                       of Poly(hexamethylene adipamide)                                              Radiation       1 Hour                                                        Example Treatment   pg/ml     k.sub.t                                                                              D.sub.t                                  ______________________________________                                        68      None        9.8E+04   -0.19  0.00                                     69      4.0 J/cm.sup.2 /side                                                                      1.0E+02    2.80  2.99                                     IC      None        1.2E+05   -0.28  -0.09                                    UC      None        0.0E+O    NA     NA                                       ______________________________________                                         Initial concentration C. albicans = 6.3E+04 cfu/ml                       

                  TABLE XI                                                        ______________________________________                                        Activity of Irradiated Spunlaced Fabric                                       of Poly(hexamethylene adipamide)                                              to Bacillus circulans spores.                                                 Radiation        1 Hour                                                       Example Treatment    cfu/ml    k.sub.t                                                                             D.sub.t                                  ______________________________________                                        70      None         1.5E+03   0.27  0.00                                     71      2.66 J/cm.sup.2 /side                                                                      2.0E+01   2.14  1.88                                     IC      None         2.5E+03   0.04  -0.22                                    UC      None         0.0E+0    NA    NA                                       ______________________________________                                         Initial Concentration B. circulans = 2.8E+03 cfu/ml                      

                  TABLE XII                                                       ______________________________________                                        Activity of Irradiated Yarn                                                   of Poly(hexamethylene adipamide)                                              to Bacteriophage T4.                                                          Radiation       1 Hour                                                        Example Treatment   pg/ml     k.sub.t                                                                              D.sub.t                                  ______________________________________                                        72      None        2.48E+05  -0.16  0.00                                     73      12 J/cm.sup.2                                                                             0.00E+00   5.23  5.39                                     IC      None        2.96E+05  -0.24  -0.07                                    ______________________________________                                         Initial Concentration Bacteriophage T4 = 1.7E+05 plaque forming units         (pfu/ml).                                                                

EXAMPLES 74 and 75

Comparable antimicrobial activity against Staphylococcus aureus andEscherichia coli was evident in experiments similar to those describedfor A. niger as detailed in Table IX. Within 24 hours, a S. aureuspopulation was reduced from 7.51E+03 cfu/ml to <10 cfu/ml, i.e. agreater than 3.9 log kill. A population of E. coli was similarly reducedfrom 1.05E+05 cfu/ml to <10 cfu/ml, i.e. a greater than 5 log kill.

COMPOSITIONS CONTAINING SUBSTITUTED UREA GROUPS EXAMPLE 76

Urea-formaldehyde resin solution (available from Cargill, Inc.Minneapolis, Minn. 55440) was dried by evaporating the solvent,suspended, and then stirred in deionized water for 24 hours. Ten grams(10) of solids (powder) were separated from the liquid by filtration anddried in air at ˜35° C.

The mass of polymer was then divided into two, five-gram batches. Onebatch was reserved as a control (Sample 10987-49-6 in Table XIII). Theother batch was irradiated according to the following procedure.

Five grams of polymer powder were placed into a 250 ml beaker. Thebeaker was secured to a ring stand at its top, and the beaker wasmounted on a test-tube vortexing device in order to rapidly vibrate thevessel in a circular motion about its vertical axis. In so doing, thepowder contained in the beaker underwent rapid convection thuscontinually renewing the powder surface.

The top of the flowing powder bed was then irradiated in air using aLambda-Physik, Excimer Laser, Model LPX 325iCC which emitted photonshaving a wavelength of 193 nm. The laser power delivered to the powdermass equaled 20 watts for a period of 10 minutes. The laser energy wasdelivered in a pulsed fashion, each pulse lasting 16 nanoseconds, at arate of 100 hertz. The laser treated powder is identified as Sample10987-49-5 in Table XIII.

The two powder samples were then tested for antimicrobial propertiesusing the following procedures. Both the control powder and theirradiated powder were separately suspended in liquid phosphate bufferfor twenty-four hours in order to extract any leachable toxins which mayhave been present. Both powder samples were then filtered from theextraction liquid, suspended in fresh phosphate buffer and then testedfor antimicrobial activity against Klebsiella pneumoniae using the ShakeFlask Test.

The antimicrobial results are shown in Table XIII, below.

                  TABLE XIII                                                      ______________________________________                                        control polymer  irradiated polymer                                           (10987-49-6)     (10987-49-5)                                                 solid    liquid      solid       liquid                                       kt   kt      kt      kt    kt    kt    kt    kt                               @1   @24     @1      @24   @1    @24   @1    @24                              hour hrs.    hour    hrs.  hour  hrs.  hour  hrs.                             ______________________________________                                        0.33 0.34    0.42    0.38  1.47  5.04  0.37  0.24                             ______________________________________                                    

HIGH ENERGY ELECTRON BEAM IRRADIATION EXAMPLES EXAMPLE 77 to 107

The following examples illustrate the preparation of antimicrobialpoly(hexamethylene adipamide) articles using a high energy electron beamsource.

The irradiated articles were either spunlaced poly(hexamethyleneadipamide) fabric: (poly(hexamethylene adipamide) fibers soldcommercially by E. I. du Pont de Nemours and Company, as style 200SDhaving a dpf of 1.8 (0.2 Tex) were spunlaced to yield a fabric), andidentified as "S-1" or "S-2" in Table XIV, or poly(hexamethyleneadipamide) membrane sold commercially as "Genescreen" by E. I. du Pontde Nemours and Company and identified as "G" in Table XIV.

For all examples shown in Table XIV, the electron beam accelerator,available from High Voltage Inc., Model KS, was operated using thefollowing settings and conditions. The electron beam accelerator had anoutput of 3 MeV electrons with a total beam current of 0.6 amp. Thewidth of the beam was 15 inches, and the distance of the beam to thesample window was set at 6 inches. The conveyor belt speed was 93inches/minute. The samples were placed flat on the conveyer belt andpassed under the beam window by mechanical operation of the belt. Ateach pass through the beam window, the delivered dose was 0.5 MRad. Thesamples had enough cumulative passes to achieve the desired final dose.For the examples in Table XIV, the fabric or membrane (2.0 g, 20×24 cm²)was sealed inside two thin bags. The inner bag was zip-lockedpolyethylene, and the outer bag was aluminized "Tyvek". Some spunlacedfabric samples were sealed under a blanket of nitrogen or argon, butmost samples were sealed under a normal air atmosphere. For deliveredbeam dosages which exceeded 20 MRad, typical exponential kill values forKlebsiella pneumoniae were 5.00 kt at 24 hr microbe contact time.

                                      TABLE XIV                                   __________________________________________________________________________    (Antimicrobial Activity Associated with                                       Poly(hexamethylene adipamide) Irradiated with High                            Energy Electrons                                                              Ex.                                                                              Art..sup.1                                                                            Beam                                                                              Radiation                                                                           Dose  Initial                                                                             kt                                           #  Type                                                                             Atmos..sup.2                                                                       Passes                                                                            Delivered                                                                           (Mrad).sup.3                                                                        cfu/mL.sup.4                                                                        @24 h                                        __________________________________________________________________________    77 S-1                                                                              Air  0   0           4.00E+04                                                                            -0.65                                        78 S-1                                                                              Air  0   0           1.20E+05                                                                            -0.62                                        79 S-2                                                                              Air  0   0           1.20E+05                                                                            -0.83                                        80 S-1                                                                              Air  5   2.5         1.20E+05                                                                            -0.52                                        81 S-1                                                                              N2   5   2.5         1.20E+05                                                                            0.32                                         82 S-2                                                                              Air  5   2.5         1.20E+05                                                                            -0.54                                        83 S-2                                                                              N2   5   2.5         1.20E+05                                                                            -0.58                                        84 S-1                                                                              Air  6   3.0         9.4E+04                                                                             2.55                                         85 S-1                                                                              Ar   6   3.0         9.4E+04                                                                             1.16                                         86 S-1                                                                              Air  20  10          1.20E+05                                                                            0.32                                         87 S-1                                                                              N2   20  10          1.20E+05                                                                            0.47                                         88 S-2                                                                              Air  20  10          1.20E+05                                                                            0.36                                         89 S-2                                                                              N2   20  10          1.20E+05                                                                            -0.24                                        90 S-1                                                                              Air  40  20          1.20E+05                                                                            0.89                                         91 S-1                                                                              N2   40  20          1.20E+05                                                                            3.14                                         92 S-2                                                                              Air  40  20          1.20E+05                                                                            4.30                                         93 S-2                                                                              N2   40  20          1.20E+05                                                                            1.25                                         94 S-1                                                                              Air  60  30          1.20E+05                                                                            5.08                                         95 S-1                                                                              N2   60  30          1.20E+05                                                                            5.08                                         96 S-1                                                                              N2   60  30          1.10E+05                                                                            5.04                                         97 S-2                                                                              Air  60  30          1.20E+05                                                                            5.08                                         98 S-2                                                                              N2   60  30          1.20E+05                                                                            5.08                                         99 S-1                                                                              N2   100 50          1.10E+05                                                                            5.04                                         100                                                                              S-1                                                                              N2   110 55          1.10E+05                                                                            5.04                                         101                                                                              S-1                                                                              Air  120 60          1.20E+05                                                                            5.08                                         102                                                                              S-1                                                                              N2   120 60          1.20E+05                                                                            2.20                                         103                                                                              S-2                                                                              Air  120 60          1.20E+05                                                                            4.54                                         104                                                                              S-2                                                                              N2   120 60          1.20E+05                                                                            5.08                                         105                                                                              S-1                                                                              N2   170 85          1.10E+05                                                                            5.04                                         106                                                                              S-1                                                                              N2   180 90          1.10E+05                                                                            5.04                                         107                                                                              G  N2   60  30          1.10E+05                                                                            4.26                                         __________________________________________________________________________     NOTES FOR TABLE:                                                              .sup.1 Article Type: S: spunlaced poly(hexamethylene adipamide)               G: "GeneScreen1: washed with "Tide" to remove fabric finishes. 2: washed      with hot water to remove fabric finishes.                                     .sup. 2 Atmosphere: Air; Nitrogen (N2); or Argon (Ar).                        .sup.3 1.0 MRad = 10 Joules/g.                                                .sup.4 Klebsiella pneumoniae as the test microbial population            

LOW ENERGY ELECTRON BEAR IRRADIATION EXAMPLES EXAMPLE 108

An approximately 8 inch×8 inch square of spunlaced poly(hexamethyleneadipamide) fabric: (poly(hexamethylene adipamide) fibers soldcommercially by E. I. du Pont de Nemours and Company, as style 200SDhaving a dpf of 1.8 (0.2 Tex) were spunlaced to yield a fabric), andhaving a basis weight of 0.95 ounce/square yard was cleaned with hotwater to which 0.25 g/L of "Merpol HCS" surfactant, sold by E. I. duPont de Nemours and Company, had been added. The fabric was treated onboth sides by the low energy electron beam apparatus in the mannerdescribed previously under Testing Conditions. The filament current wasset to 0.9 amperes, the beam voltage was maintained at 500 volts, theplaten was rotated at 60 rotations per minute, and the treatmentcontinued for 15 seconds. Examination by X-ray PhotoelectronSpectroscopy (XPS) of a sample cut from the region that had passeddirectly over the filament assembly showed a decrease in the fraction ofthe carbon 1s peak attributable to carbonyl from 13-14% to 10-12%. Inthe Shake Flask Test for antimicrobial activity, the material taken fromthe region that passed directly above the filament reduced theKlebsiella pneumonias population 2.84 logs in one hour and eliminatedthe population entirely in 24 hours (a 4.75 log reduction).

EXAMPLE 109

An approximately 8 inch×8 inch square of spunlaced poly(hexamethyleneadipamide) fabric: (poly(hexamethylene adipamide) fibers soldcommercially by E. I. du Pont de Nemours and Company, as style 200SD,having a dpf of 1.8 (0.2 Tex) were spunlaced to yield a fabric), andhaving a basis weight of 0.95 ounce/square yard was cleaned with hotwater to which 0.25 g/L of "Merpol HCS" surfactant had been added. Thefabric was treated in the same manner as described in Example 108,except that the treatment time was 150 seconds. The ring of materialthat had passed directly over the filament was light tan instead of theoriginal white. The x-ray photoelectron spectrum of the carbon 1s peakcould not be separated into carbonyl and aliphatic components using theparameters applied to material treated for 15 seconds. Accounting forall the spectral intensity required introduction of a third component orchanging the parameters for carbonyl components by more than 20%. Thesurface chemistry of this material is therefore different from that ofthe other materials. In the Shake Flask Test for antimicrobial activity,a 0.13 log decrease in the Klebsiella pneumoniae population occurredafter one hour, and there was a 0.37 log increase after 24 hours.

EXAMPLE 110

An approximately 8 inch×8 inch square of spunlaced poly(hexamethyleneadipamide) fabrics: (poly(hexamethylene adipamide) fibers soldcommercially by E. I. du Pont de Nemours and Company, as style 200SDhaving a dpf of 1.8 (0.2 Tex) were spunlaced to yield a fabric) andhaving a basis weight of 0.95 ounce/square yard was cleaned with hotwater to which 0.25 g/L of "Merpol HCS" surfactant had been added. Thefabric was treated in the same manner as described in Example 108,except that the treatment time was 2 seconds. X-Ray PhotoelectronSpectroscopy (XPS) showed a fraction of the carbon Is peak attributableto carbonyl of 13%. In the Shake Flask Test for antimicrobial activity,the Klebsiella pneumoniae population was reduced by 2.09 logs in onehour and 3.01 logs after 24 hours.

CHEMICAL REDUCTION EXAMPLES

In the following examples, polyamide fiber was treated with differentchemical reagents and subsequently tested for antimicrobial activity. Ineach of the following examples, the fiber was scoured as follows.

To 1000 ml of deionized water, 0.25 g of the surfactant, "Igepon T-51"available from GAF Corp., was added. The fiber was then added, and themixture was brought to a slow boil. The mixture was then stirred with aglass rod intermittently for at least 15 min. The fiber was then removedand washed while squeezing, in cold tap water for 5 min and then washedwith deionized water for 2 min. The fiber was then air-dried overnight.

EXAMPLE 111

About 200 ml of dry tetrahydrofuran (THF) was added to a dry 500 mlthree necked round bottom flask fitted with an overhead stirrer with aglass paddle. After the system was flushed with nitrogen, 1.0 g oflithium aluminum hydride (LiAlH₄), available from Aldrich Chemical Co.,Milwaukee, Wis. was added gradually and allowed to stir for 45 minutes.When the 45 min was over, 5.0 g of nylon fiber, 6 denier per filament (6dpf) nylon 66 staple type 110, available from E. I. du Pont de Nemoursand Company, that had been scoured and dried overnight in a vacuum ovenat 50° C. was added and the paddle was manipulated so that the fiber wascompletely immersed. Some additional solvent was required to insurecomplete immersion of the fiber. The reaction was allowed to stirovernight at room temperature under a nitrogen blanket. The reaction wasworked up by dropwise sequential addition of excess(˜30 ml each)acetone, n-propyl alcohol, water, and a 9:1 mixture of water:formic acidwith stirring during the additions. The fiber was then rinsedextensively with water, 10% ammonium hydroxide, and then again withwater and dried. The Shake Flask Test results for Klebsiella pneumoniaeare given in Table XV.

EXAMPLE 112

About 5.0 g of 1200 denier "Anso IV" 6 nylon BCF, available from AlliedChemical Co., was treated in the same manner as described in Example111. The Shake Flask Test results for Klebsiella pneumoniae are given inTable XV.

Comparative Example 113

5.0 g of nylon fiber, 6 denier per filament (6 dpf) nylon 66 staple type110, available from E. I. du Pont de Nemours and Company, were treatedin the same manner as described in Example 111, except a 3:1 mixture ofdiethyl ether:methyl alcohol was used as a solvent and 1.0 g of sodiumborohydride was used rather than the lithium aluminum hydride (LiAlH₄).The Shake Flask Test results for Klebsiella pneumoniae are given inTable XV.

Comparative Example 114

About 5.0 g of nylon fiber, 6 denier per filament (6 dpf) nylon 66staple type 110, available from E. I. du Pont de Nemours and Company,were treated with 0.8% sodium borohydride solution and wrung out to 70%liquid absorption. The sodium borohydride was not washed out after thetreatment and the strips were dried for 20 minutes at 105° C. The fiberwas then rinsed with water. After drying, the strips were heated to 150°C. The Shake Flask Test results for Klebsiella pneumoniae are given inTable XV.

                  TABLE XV                                                        ______________________________________                                                    1 hr       24 hr                                                  Example                                                                              Sample ID  kt       Dt    kt     Dt                                    ______________________________________                                        111    P11037-14  2.42     2.53  4.54   4.84                                  112    P11037-14-1                                                                              4.30     4.41  5.08   5.38                                  113    P11037-15-1                                                                              0.15     0.27  -0.50  -0.20                                 114    P11037-17  0.03     0.14  0.32   0.62                                  115    Control    -0.11    0.00  0.30   0.00                                         scoured 66                                                                    nylon                                                                  ______________________________________                                    

We claim:
 1. A process for preparing an inherently antimicrobial,polymeric material, comprising irradiating the surface of a shapedmaterial comprising an organic polymer having carbonyl groups covalentlybound to nitrogen in the form of ##STR4## moieties, said material beingin a form having a specific surface area such that at least 0.02 m² /gof the material is irradiated with an ultraviolet photon energy densityof at least 300 mJ/cm² at a wavelength of no greater than 222 nm andwherein the absorption coefficient for the material is at least 1,5/D,where D is the thickness of the material, whereby said irradiationconverts a sufficient amount of said ##STR5## moieties on the surface ofsaid material to amine or hydrazine moieties to impart antimicrobialactivity substantially to the surface of said material, said polymerbeing selected from the group consisting of a polyamide, polyurea,polyhydrazide, polyurethane, and copolymers and polymer blends thereof.2. A process for preparing an inherently antimicrobial, polymericmaterial as defined in claim 1, wherein the source of ultravioletphotons is a laser.
 3. A process for preparing an inherentlyantimicrobial, polymeric material as defined in claim 1, wherein thesource of ultraviolet photons is an ultraviolet lamp.
 4. The process ofclaim 1, wherein the polymer is a polyamide.
 5. A process for preparingan inherently antimicrobial, polymeric material, comprising irradiatingthe surface of a shaped material comprising an organic polymer havingcarbonyl groups covalently bound to nitrogen in the form of ##STR6##moieties, said material being in a form having a specific surface areasuch that at least 0.02 m2/g of the material is irradiated withelectrons having a kinetic energy of about 6 eV, to 10,000,000 eV at anenergy absorption from the electrons of about 10,000 erg/cm³ to1,000,000 erg/cm³, whereby said irradiation converts a sufficient amountof said ##STR7## moieties to amine or hydrazine moieties to impartantimicrobial activity to the surface of said material, said polymerbeing selected from the group consisting of a polyamide, polyurea,polyhydrazide, polyurethane, and copolymers and polymer blends thereof.6. The process of claim 5, wherein the surface of the shaped material isirradiated with electrons having a kinetic energy of 100 to 5000 eV, atan energy absorption from the electrons of 50,000 to 250,000 erg/cm³ ofirradiated volume.